The present invention relates to an arrangement for the actuation of a gas-exchange disk or poppet valve longitudinally guided in the cylinder head of a reciprocating piston engine with two electromagnets which are alternately periodically energized and thereby move to and fro an armature against the force of a cylindrical torsion rod spring that opens and closes the disk valve.
Such an actuating arrangement is described in the patent application No. P 36 16 540.9-13. The gas-exchange valve is actuated by two electromagnets operating against a spring force which are alternately energized and thereby move the armature to and fro which opens and closes the disk valve. In order to keep small the moved spring masses and therewith the mass inertia of the entire actuating arrangement, a cylindrical torsion rod spring is used as spring. The torsion rod spring is non-rotatably connected at its one side at the cylinder head and at its other side with one end of a one-armed valve lever. With its other end, the valve lever pivotally engages at the valve stem of the disk valve. At a distance from this pivotal connection, the armature is attached at the valve lever. As two pivotal connecting places are present, which are always beset by manufacturing tolerances, it is difficult to so match the actual valve stroke to the armature stroke that, on the one hand, the valve is tightly closed and, on the other, no excessively large air gap remains between the armature disk and the electromagnet in the closing position.
It is the object of the present invention to so further develop such an actuating mechanism in such a manner that its moved masses are once more reduced and the function of the valve operation is assured without maintaining very narrow manufacturing tolerances.
The underlying problems are solved according to the present invention in that the valve lever is pivotally connected at its free end with the armature and in that the armature together with the armature disk concentrically secured thereat is arranged coaxially to the stem of the disk valve. If the armature together with the armature disk is disposed coaxially to the disk valve, the disk valve can be controlled by means of the armature during the energization of the electromagnets without interconnection of pivotal connecting places inherently having play. An exact coordination between armature stroke and valve stroke then exists insofar as the manufacturing tolerances of the disk valve and armature as well as the spacing tolerance from the seat of the disk valve to the end surfaces of the electromagnets are maintained.
In order to become even more independent of manufacturing tolerances and to create a stress-free compensation in case of thermal expansion of the disk valve, according to another feature of the present invention a magnetizable entrainment disk is secured at the stem end of the disk valve which is disposed with axial play between two abutment surfaces of the armature disk. The construction becomes simplest if the armature disk is formed of two circular disks and the entrainment disk is placed into the separating plane thereof with axial play relative to the end surfaces of the disks which now serve as abutment surfaces. If during the closing of the disk valve the armature disk is attracted and placed against the upper electromagnet, then the entrainment disk is subsequently pulled upwardly by the electromagnet until the disk valve closes tightly. For purposes of opening the disk valve, the upper electromagnet is de-energized and the armature disk is displaced downwardly by spring force.
The construction according to the present invention makes it possible to integrate in the simplest manner also a hydraulic damping arrangement into the actuating mechanism which prevents a hard and noisy contact of the valve disk and undesired oscillatory movements. For that purpose, the armature is provided with a central bore filled with a hydraulic liquid. A piston acting on the stem end of the disk valve is longitudinally movably guided in the central bore and in the armature disk; the piston is supported by a coil spring which abuts at a radial projection of the central bore. The central bore is provided with a ball check valve above the radial projection. The construction according to the present invention makes it possible to construct the valve lever shorter with the same valve stroke to be realized.